strerror_r: fix OpenBSD behavior on 0 OpenBSD treats strerror_r(0,,) as a success, but with a message "Undefined error: 0"; while this is distinct from strerror_r(-1,,) returning "Unknown error: -1", it does not imply success. Meanwhile, if buf is short enough for ERANGE, then we can't use strstr to look for "Unknown" or "Undefined" in the resulting message, like we had been doing for strerror(). Fix this by shifting the burden - now the strerror-override code guarantees that 0 will have an override when needed. * lib/strerror-override.c (strerror_override): Also override 0 when needed. * lib/strerror-override.h (strerror_override): Likewise. * lib/strerror.c (strerror): Simplify, now that 0 override is done earlier. * lib/strerror_r.c (strerror_r): Likewise. * m4/strerror.m4 (gl_FUNC_STRERROR): Split detection of 0 behavior... (gl_FUNC_STRERROR_0): ...into new macro. * m4/strerror_r.m4 (gl_FUNC_STRERROR_R): Replace strerror_r if 0 is overridden. (gl_FUNC_STRERROR_R_WORKS): Avoid extra tests if 0 is broken. * modules/strerror-override (Files): Add strerror.m4. (configure.ac): Also provide override for 0 when needed. * doc/posix-functions/strerror.texi (strerror): Document this. * doc/posix-functions/perror.texi (perror): Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>

#serial 7

# Copyright (C) 1998-1999, 2001, 2004, 2008-2011 Free Software Foundation, Inc.
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.

dnl based on code from Eleftherios Gkioulekas
dnl Autoconf 2.60 provides AC_HEADER_ASSERT for the same purpose, but
dnl it has broken semantics for --enable-assert until 2.64.
AC_DEFUN([gl_ASSERT],
[
  AC_MSG_CHECKING([whether to enable assertions])
  AC_ARG_ENABLE([assert],
    [AS_HELP_STRING([--disable-assert], [turn off assertions])],
    [AS_IF([test "x$enableval" = xno],
      [AC_DEFINE([NDEBUG], [1],
        [Define to 1 if assertions should be disabled.])],
      [test "x$enableval" != xyes],
      [AC_MSG_WARN([invalid argument supplied to --enable-assert])
      enable_assert=yes])],
    [enable_assert=yes])
  AC_MSG_RESULT([$enable_assert])
])